Sulfur containing lubricating oil additives



United States Patent SULFUR CONTAINING LUBRICATING OIL ADDITHVES Application September 27, 1954 Serial No. 458,672

is Claims. (01. 252- 47 No Drawing.

Our invention relates to novel compositions of matter, alkyl disulfide derivatives of thiocyanic acid polymers, which by reason of oil solubility, stability and oxidation inhibiting properties have special value as lubricating oil additives.

We have discovered that alkyl disulfides of thiocyanic acid polymers may be produced by reaction of alkyl sulfenyl chlorides With dithiocyanic acid. When the latter is prepared conventionally by reaction of ammonium thiocyan'ate and acetic anhydride, the reaction product appears to .be a mixture, predominating in the alkyl disulfide derivative of dithiocyanic acid, i. e. an alkyl dithio- 1,3-diazene (or diazete). The reaction mixture also contains from about 15% to 50% of the alkyl disulfide derivative of trithiocyanuric acid, 'i.- e. an alkyl dithio- 1,3,5-tniazine, and may contain some more highly polymerized material. The probable structures of the 2.main constituents which may be isolated from the reaction Iture are as follows:

"l'iibitor has the particular advantage of containing sulfur in a form that is non-corrosive to copper and silver bearing surfaces, which normally present a special problem with sulfur containing inhibitors, while combining high capacity as an oxidationinhibitor with efiective load bearin'g capacity.

"Our invention includes alkyl dithio/polythiocyalnates as such and in admixture. The alkylsubstituents are selected with a view to providing practicable oil solubility. 'In general, "disulfide derivatives in which all of the disulfide groups are linked to alkyl substituents are preferred, i. 'e. 2,4-bis(alkyl-dithio) 1,3 diazenes (or diazetes). The alkyl 'substituent may beselected according to availability =of alkyl sulfenyl halide starting material and ease of preparation, bearing in mind the requirement that sufficient oil solubility for the desired level of use must be imparted to the heterocyclic ring structure. Thus, with the trisand bis-derivatives, lower alkyl substituents such as n-butyl groups may be employed. If the molecule contains'only one alkyl substituent, on the other hand, it is advisable to employ a longer chain alkyl group e. ,g. a dodccyl or octyl group. As a general guide to oil solubility permitting preparation of concentrates of the additives for use in blending operations, it is desirable to provide a total of or more carbon atoms in the diazine molecule and or more carbon atoms in the triazine 2,4,6-tris(alkyl-dithio) l,3,5-triazines and molecule. In addition to alkyl groups, equivalents such as cycloalkyl and alkyl aryl may be employed.

In the preparation of the new alkyl disulfide derivatives, either dithiocyanic acid or trithiocyanuric acid may be employed as starting material, depending upon whether alkyl dithiotriazinesor alkyl dithiodiazetes are desire'd. The starting acids .may be prepared from ammonium 'thiocyanate and acetic anhydride by warming the mixture and pouring the reaction mass into cold water. The crystalline reaction product maybe purified by alkaline extraction and reprecipitation with a mineral acid. A reaction product, predominating in either dithiocyanic acid or trithiocyanuric acid can'be prepared from ammonium thiocyanate and acetic anhydride by varying the reaction conditions. If dithiocyanic acid. is theproduct desired, the reaction is conducted at a temperature approximating steam bath temperatures. .If the reaction product desired is the trithiocyanuric acid, a temperature in the range of .3070 C. is preferred. Either' form of free acid can be recovered from the crystalline reaction product by fractional crystallization and/ or selective adsorption methods. On the other hand, we have found that the primaryie action mixture can be converted to an alkyl disulfide derivative of high activity as a bearing corrosion inhibitor. Trithiocyanuric acid also may beprepared directly by reaction of a cyanuric halide with potassiumhydrosulfide.

The thiocyanic acid starting material is convertedto the. desired disulfide derivative by reaction with :an alkyl ,sulfenyl halide. For example,lthe thiocyanic acid starting material may be contacted .at reduced temperature with the-alkyl sulfenyl halide .by addingthelatter atza controlled rate to a-"suspension of the thiocyanic facid starting material in an inert organic solvent. 'A=stoichiometric ratio of reactants is selected to provide the degree of alkyl substitution desired in the product. .The :new productsin general are dark colored viscous liquids which are recovered by strippingthe solvent from the reaction mixture.

When the alkyl disulfide derivatives are incorporated in lubricating oils, the resulting composition shows improved oxidation stability and load carrying capacity. For use primarily as an antioxidant, the .new additives may the employed, for example, in amounts approximating 0.001 to'5.0 weight percent in circulating oils,.transformer oils, white oils, cutting oils and the like. For use as hearing corrosion .inhibitors in engine oils, about 0.05 to .10 weight percent advantageouslyis employed. I For applications Where enhancement in E. P. properties is desired, upwards of about 0.1 weight percentof the additive should be used. 7

In many lubricating applications, oil blends containing more than one additive are employed. The new additives may be used in conjunction with conventional additives such as pour depressors, viscosity. index improvers, oiliness agents, foam suppressors and the like. The new additives have the special advantage in heavyduty engine oils that they may be used as inhibitors with sulfurized andphosphosulfurized additives of the active. sulfur type. For example, sulfurized dipentene isan active oxidation inhibitor which also imparts improved load carrying capacity to engine oil compositions. Anroil containing sulfurized dipentene (or other sulfurized or phosphosulfurized additive of theactive sulfur type) may be too corrosive toward copper and silver bearing surface materials to satisfy specifications for certain types of service. We have found that oil blends containing additives ofthis type together with the new additives combine ahigh degree of inhibiting and load bearing effectiveness and yet are non-corrosive toward copper and silver. 'The new additives may be further sulfurized by heating with-sulfur. .The resulting products exhibit corrosion inhibiting and E. P. properties, and have particular value in cutting oil formulations.

The invention will be further described by illustration in the form of specific examples of preparation, testing and use of the new additives. In the examples, several tests are referred to as the SSCT, EMD and L-4 .engine tests. e

The SSCT test was runas follows: A copper-lead test specimen is lightly abraded with steel wool, washedwith naphtha, dried and weighed to the nearest milligram. The cleaned copperlead test specimen is suspended in a steel beaker, cleaned with a hot tri-sodium phosphate solution, rinsed with water and acetone and dried. 250 grams of the oil to he tested together with 0.625 gram lead oxide and 50 grams of a 30-35 mesh sand are charged to the beaker. The beaker is then placed in a bath or heating block and heated to a temperature of 300 F. (12 F.) while the contents are stirred by means of a stirrer rotating at 750 R. P. M. The contents of the beaker are maintained at this temperature for twentyfour hours, after which the copper-lead test specimen is removed, rinsed with naphtha, dried and weighed. The test specimen is then replaced in the beaker and an additional 0.375 gram of lead oxide added to the test oil. At the end of an additional twenty-four hours of test operation the test specimen is again removed, rinsed and dried as before, and weighed. The test specimen is again placed in the beaker together with an additional 0.250 gram of lead oxide and the test continued for another twenty-four hours (seventy-two hours total). At the conclusion of this time, the test specimen is removed from the beaker, rinsed in naphtha, dried and weighed. The loss in weight of the test specimen is recorded after each weighing. A weight loss of 200 mg. or less in 48 hours and 500 mg. or less in 72 hours is allowable.

In the EMD test a silver strip 2 cm. x 5.5 cm. with a smallhole at one end for suspension is lightly abraded with No. steel wool, wiped free of any adhering steel wool, washed with carbon tetrachloride, air-dried and then weighed to 0.1 milligram. Three hundred cc. of the oil to be tested is placed in a 500 cc. lipless glass beaker and the oil is heated to a temperature of 300 F. (i2 F.) and the silver test strip suspended in the oil so that the strip is completely immersed therein. The oil in the beaker is stirred by means of a glass stirrer operating at 300 R. P. M. At the end of twenty-four hours, the silver strip is removed and while still hot rinsed thoroughly with carbon tetrachloride and airdried. The appearance of the strip is then visually noted and given ratings according to the following scale:

1--Bright 2Stained 3Grey-black 4-Black, smooth 5-Black, flake After the visual inspection the silver strip is immersed in a potassium cyanide solution at room temperature until the silver surface assumes its original bright or silver appearance. The silver strip is then washed successively with distilled water and acetone, air-dried and weighed. A weight loss of 20 mg. or less is considered passing.

The L-4 engine test followed the procedure specified by C. R. C. designation L-4-545, C. R. C. Handbook, 1946 edition, Coordinating Lubricants Research Council, New York, N. Y.

Example I Dodecyl sulfenyl chloride was prepared by adding 1.4 mole of chlorine to 282 grams of n-dodecyl mercaptan in carbon tetrachloride solution at 0 C. This solution was then added to 74.6 grams of dithiocyanic acid suspended in carbon tetrachloride and stirred at 0-10 C. for two hours. Dioxane was then added, and

the mixture was allowed to stir at room temperaturefor two hours. The product was washed successively with 10% sodium hydroxide and with water, and finally was stripped with nitrogen at 200-220 F. for one hour. The product was 306 grams of a dark brown liquid containing 20.4% S and 2.88% N. A solvent extracted SAE-30 grade oil containing 0.75% of the above product and 3.3% of a barium salt of a reaction product of phosphorous pentasulfide and a butylenes polymer gave a bright strip in the EMD silver test, and SSCT losses of 3 mg. at 48 hours and 28 mg. at 72 hours.

Example II The reaction of n-butyl sulfenyl chloride with dithiocyanic acid was carried out by the process outlined in Example I above. The product was a dark brown liquid containing 39.4% S and 5.52% N. This liquid was tested at0.43% in solvent extracted SAE-30 grade oil containing 3.3% of a barium salt of a reaction product of phosphorous pentasulfide and a butylenes polymer. The finished oil gave a bright EMD silver strip, and SSCT weight losses of 1 mg. at 48 hours and 26 mg. at 72 hours.

The product of Example II was run in the L-4 engine test at 0.15% concentration plus 0.75 of sulfurized dipentene and 3.3% of a barium salt of a reaction product of phosphorous pentasulfide and a butylenes polymer in a solvent extracted Mid-Continent SAE-30 grade oil. The test gave light brown bearings with weight losses of 0.07, 0.06, and 0.14 gram (allowable weight loss is 0.20. gram average). The same blend gave a bright strip in the EMD silver corrosion test.

In Examples land 11 above, the dithiocyanic acid was prepared by reaction of ammonium thiocyanate and acetic anhydride. The materials, 62 grams of ammonium thiocyanate and 87 grams of acetic anhydride, were heated to steam bath temperature with occasional stirring for one hour. The reaction mixture was poured into cold water and the resulting crystals were filtered from the liquid. The dry product was dissolved in sodium hydroxide solution and precipitated with hydrochloric acid. The crystals were washed with water and dried. The yield was 13.2 grams.

The above preparation was found to yield a mixture of products when a typical reaction product was characterized by a process involving recrystallization, methylation, and chromatographic separation. In the following procedure the yield of trithiocyanuric acid was increased at the expense of dithiocyanic acid.

Example III A mixture of 1 mole ammonium thiocyanate and 1.4 moles acetic anhydride was stirred at 75-80" C. for 1 hour, then poured into 1 liter cold water. The solid product was collected on a filter, washed with water, dissolved in aqueous sodium hydroxide, filtered, and precipitated with hydrochloric acid. A 20.35 gram sample of the dried precipitate was dissolved in 300 ml. of water to which 28 ml. of 20% sodium hydroxide had been added. The reaction mixture was held at 13-20 C. while 18 ml. of dimethyl sulfate was added in three portions. Ten more ml. of sodium hydroxide solution was then added to bring the mixture back on the alkaline side. After vigorous stirring the solid reaction product was filtered off and dried (11.85 grams). The dry solid was dissolved in benzene, filtered, washed with 10% sodium hydroxide and washed with water, dried, and filtered. The benzene solution was chromatographed on activated alumina, and the chromatogram was developed with benzene, and ethyl acetate in benzene. Six cuts were obtained. The first two of these were combined and recrystallized three times from benzene. A white crystalline compound was obtained (3.0 grams), M. P. 189-192 C.

Analysis.-Calculated for O I-1 1N 8 trimethyl trithiocyanurate: DQ312188; H, 4.12; S, 43.82; N, 19.18; mol. Wt., 225. Found: C, 33295;"H,"4. 33; 5, 13.60; N, 19.06; 11101. Wt., 2l9.

i Example IV Trithiocyanuric acid was prepared *by the action of (potassium .hydrosulfide on cyanuricschloride. nf'Aa'ipotassium hydrosulfide solution,-prepar.ed by adding 517 grams of potassium hydroxide'to 3litfers of'wa'ter saturated with hydrogen sulfide, f wa's'l tr'e'ate'dwith 263*;8 "grams of- "cyanuric chloride in portions over onei' hour. .Themixture was stirred for three days at room temperature, the product precipitated by the addition of 375 ml. of hydrochloride acid, the precipitate collected on a filter and washed with water. The product was dissolved in aqueous sodium hydroxide and reprecipitated with acetic acid, washed and dried (yield, 172.4 grams). A solution of n-dodecyl sulfenyl chloride, prepared by dissolving 289 grams of n-dodecyl mercaptan in 600 ml. of carbon tetrachloride and chlon'nating at 5 C. to 0 C. with gaseous chlorine, was run slowly into 74.5 grams of the above trithiocyanuric acid suspended in 300 ml. of carbon tetrachloride. After one hour, dioxane was added and the mixture allowed to stir at room temperature for 16 hours more. The mixture was then diluted with water, washed with 10% sodium hydroxide and with water, and stripped at 220 F. with nitrogen. The product was a clear, amber liquid, Weighing 336 grams, and containing 3.9% nitrogen and 21.6% sulfur.

A solvent extracted SAE-SO grade oil was made up containing 0.75% of above product and 3.3% of a barium salt of a reaction product of phosphorus pentasulfide and a butylenes polymer. The finished oil was non-corrosive to silver in the EMD test (giving a bright strip), and gave SSCT bearing weight losses of 12 mg. at 24 hours, 23 mg. at 48 hours, and 31 mg. at 72 hours.

Example V Following the procedure of Example III, ammonium thiocyanate was reacted with 1.4 parts of acetic anhydride by heating to 70 C. The reaction initiated with vigorous evolution of gases. After the initial reaction had subsided, the mixture was heated at 80 C. until the reaction was completed. A portion of the product was treated with lauryl sulfenyl chloride according to the procedure of Example I. The resulting product was subjected to infra-red analysis. The spectrum was practically identical with that of the product obtained from Example IV above, namely, the reaction product of lauryl sulfenyl chloride with trithiocyanuric acid prepared from cyanuric chloride and potassium hydrosulfide.

Example VI Percent Concentratlon Dlsulfide Derivative EMD mg. loss 0.8 bright strip. 4.7. 27.

SSCT results on these blends showed that the superior effectiveness of the sulfurized dipentene as a bearing corrosion inhibitor was not lessened by the addition of these agents although its corrosiveness to silver was significantly reduced.

Example VII The -t'riazine itris lauryldisulfide :described in. Example IV Iabove was :used I to I-deactivate a solvent extracted 'SAE-30igrade -oil:conta.ining.-3.'3% of' a'ba'ri'nm salt of a reaction product 0f phosphorus pentasulfide and -la .butylenes polymer aud 10.75% :of "sulfurized dipentene.

The vuudeactivated oilrgave 1100 mg. silver-loss in the EMD'ICSI. Addition 10f --0.2% of thetriswlauryldisulfide reduced silver corrosion qto 51 11611301111. where the -test; strip was-only veryrslightly stained. The deactivated, oilitgave SSCT weight losses -of -2-1-mg.-at-48. hoursl-and .33; mg.

at 72 hours.

Example VIII Example IX A 7.80 grams sample of the product described in Example IV above was heated with 1.92 grams of sulfur at C. for 1% hours. The product was a dark brown oil containing 27.2% S. A solvent extracted SAE-30 grade oil containing 0.75% of this sulfurized material and 3.3% of a barium salt of a reaction product of phosphorus pentasulfide and a butylenes polymer gave SSCT weight losses of 76 mg. at 48 hours and 96 mg. at 72 hours.

We claim:

1. An oil soluble alkyl disulfide of a compound selected from the group consisting of 1,3-diazete and 1,3,5-triazine.

. An oil soluble alkyl disulfide of 1,3,5-triazine.

. 2,4,6-tris(alkyl-dithio)-1,3,5-triazines. 2,4-bis(alkyl-dithio)-1,3-diazetes.

. 2,4,6-tris (n-butyl-dithio)-1,3,5-triazine. 2,4,6-tris(lauryl-dithio)-1,3,5-triazine. 2,4,6-tris(t-octyl-dithio)-1,3,5-triazine. 2,4-bis(dodecyl-dithio)-1,3-diazete.

9. 2,4-bis(n-butyl-dithio)-1,3-diazete.

10. A lubricating oil composition which essentially comprises a mineral lubricating oil and an oil soluble alkyl disulfide of a 1,3,5-triazine in an amount suflicient to impart to the lubricating oil improved bearing corrosion properties.

11. A lubricating oil composition which essentially comprises a mineral lubricating oil and an oil soluble alkyl disulfide of a 1,3-diazete in an amount suflicient to impart to the lubricating oil improved bearing corrosion properties.

12. A lubricating oil composition which essentially comprises a mineral lubricating oil and a 2,4,6-tris(alkyldithio)-1,3,5-triazine in an amount suflicient to impart to the lubricating oil improved bearing corrosion properties.

13. A lubricating oil composition which essentially comprises a mineral lubricating oil and a 2,4-bis(alkyldithio)-1,3-diazete in an amount suificient to impart to the lubricating oil improved bearing corrosion properties.

14. A lubricating oil composition which essentially comprises a mineral lubricating oil and 2,4,6-tris(n-butyldithio)-1,3,5triazine in an amount sufiicient to impart to the lubricating oil improved bearing corrosion properties.

15. A lubricating oil composition which essentially comprises a mineral lubricating oil and 2,4,6-tris(lauryldithio)-1,3,5-triazine in an amount sufiicient to impart to the lubricating oil improved bearing corrosion properties.

16. A lubricating oil composition which essentially comprises a mineral lubricating oil and 2,4,6-tris(t-octyl- References Cited in the tile of this patent .dithio)-1,3,5-triazine in, an amount sufiicient to impart t0 I V UNITED STATES PATENTS the lubricating oil improved bearing corrosion properties.

17. A lubricating oil composition which essentially A 211o281 Adams.

comprises a mineral lubricating oil and 2,4-bis(dodecyl- 2'676151 Lough! ct dithio)-l,3-diazete in an amount suflicient to impart to V FOREIGN PATENTS the lubricating oil improved bearing corrosion properties. 580,405 Great Britain Sc 6 1946 18. A lubricating oil composition which essentially comprises a mineral lubricating'oil and 2,4-bis(n-butyl- 4 r OTHER REFERENCES -dithio)-1.3-diazete in an amount sufi'lcient to impart to 10 Hackhs Chemical Dictionary, 3rd.ed., Blakiston Co., the lubricating oil improved bearing corrosion properties. Philadelphia, 1944, p. 266. 

1. AN OIL SOLUBLE ALKYL DISULFIDE OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF 1,3-DIAZETE AND 1,3,5-TRIAZINE,
 10. A LUBRICATING OIL COMPOSITION WHICH ESSENTIALLY COMPRISES A MINERAL LUBRICATING OIL AND AN OIL SOLUBLE ALKYL DISULFIDE OF A 1,3,5-TRIAZINE IN AN AMOUNT SUFFICIENT TO IMPART TO THE LUBRICATING OIL IMPROVED BEARING CORROSION PROPERTIES. 